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Old 06-19-2019, 11:05 PM   #5
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 43,242
 

2003 L-Series 3.0L Sedan
Default Re: BCM problem I think - need advice

There are two voltage regulators, alternator - regulated between 12v-15v and 5v regulator in each control module requiring 5v for logic level signals. The ubiquitous 12v to 5v voltage regulator are part of all auto electronics where 12v-15v battery power is regulated down to 5v for integrated circuit boards. Two areas would be considered if one or both regulated voltages fails. 12v auto electric systems are generally designed to operate between a low of 9 volts to as high as 15 volts dc. Below 9v and current cannot power solenoids or dc motors. Above 15 volts and higher currents may cause overheating and damage. Electronics are strictly regulated with their own voltage regulators to prevent the same occurrence of damage. With electronics requiring 12v and 5v, any voltage deviation from minimums and maximums are handled differently. Electronics must operate in a narrow voltage range. When voltages dip too low, electronics goes to sleep - too little power reduces electronics circuit effectiveness and sluggish behavior may be seen as unusual symptoms. The easiest example of sluggish and going to sleep is our radios, running on 12v and 5v. With radio on, turn off the ignition switch (cutting power to the radio). High power circuits like the radio display dims immediately while the speakers drops volume until no more radio noise. Without skipping a beat, turning the ignition switch powers up the radio with display noise returning. The radio goes to sleep on its last setting (with standby 12v power needed to keep preset stations in 5v memory alive) and returns to the same station when main power is returned. No harm, no foul. Memory presets are lost if battery negative is disconnected. All electronics are protected against low and high voltages in most situations. Its up to the alternator voltage regulator to supply operating voltages for electronics while recharging the battery. 13v-15v is the ideal alternator regulated range with 14.7v the perfect average regulated voltage.

With electronics designed with near total reliability from years of operating in real world conditions, individual module failures can occur for any reason; poor solder joints, mechanical stress to electrical connections on circuit boards, corrosion, ic chip internal failure, etc. Voltage regulation failure my be unheard of since no one outside of bench technician knowledge of auto electronics repairs (if this exists at all) may be the only people to have opinions. Circuit boards are no longer repaired as much as the more cost effective solution is replacement. Bench technicians still exist in aviation but less so in automotive electronics. Some good examples are attempts from members here sending their ecm and bcm to third party places advertising expertise in repairs only to find Saturn modules do not lend themselves to repairs or programming. GMs scantool is the only programmer using proprietary software for programming VIN, mileage and other options for new blank modules. More for protection against tuners and thieves. Other GM vehicles do lend themselves to tuning.

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